USYD: WSD and Lexical Substitution using the Web1T corpus

This paper describes the University of Sydney’s WSD and Lexical Substitution systems for SemEval-2007. These systems are principally based on evaluating the substitutability of potential synonyms in the context of the target word. Substitutability is measured using Pointwise Mutual Information as obtained from the Web1T corpus. The WSD systems are supervised, while the Lexical Substitution system is unsupervised. The lexical sample sub-task also used syntactic category information given from a CCG-based parse to assist in verb disambiguation, while both WSD tasks also make use of more traditional features. These related systems participated in the Coarse-Grained English All-Words WSD task (task 7), the Lexical Substitution Task (task 10) and the English Lexical Sample WSD sub-task (task 17).